This invention relates to apparatus for identifying failure of charging diodes in automotive electrical systems, and particularly the charging diodes intermediate the alternator and storage battery thereof.
Conventional automotive electrical systems involve a storage battery providing DC power for engine start-up and the like, and an alternator which is mechanically driven by the operating engine, and which provides AC signals for utilization by the car. Among other applications of the AC from the alternator is the maintenance of a suitable charging level in the storage battery. Conventionally, the three phase AC alternator output is coupled to a diode network for conversion to DC, which is coupled for charging to the automotive battery. This diode network generally involves three diodes having their cathodes connected in common, and their anodes coupled to respective alternator output phrases.
It is a primary object of the present invention to provide apparatus for identifying failure of charging diodes intermediate the alternator and storage battery of an automotive electrical system.
When all three charging diodes are operating properly, each is providing the DC for approximately one third of the cycle, with a small amount of irregularity or ripple therein. This unavoidable irregularity in the signal will have an amplitude range dependent on the charge level of the battery, and the electrical load imposed on the system. Low battery charge level and other loads (e.g., auto headlights, horn, etc.) tend to burden the alternator, and under such conditions the alternator output is somewhat irregular. So long as the charging diodes are functioning properly and the storage battery is undamaged and capable of being recharged, however, the amount of ripple normally encountered in the alternator output waveform is rather small, for example on the range of 0.005 to 0.01 volts.
If one or more of the charging diodes should fail, such as due to vibration, shock, electrical burn out/failure, or the like, the alternator output waveform becomes considerably distorted, since for a substantial portion of each output waveform period, no rectified voltage is being furnished.
It is a more specific object of the present invention to detect charging diode failure at the battery terminals by discriminating excessive ripple from normal ripple in the alternator output waveform.
It is a still further object that such apparatus be compact and simple, and have sufficiently high input impedance that it provides minimal loading on the circuit being evaluated.